A space facility is a spacecraft, either one that is robotically operated or one capable of supporting a crew, which is designed to remain in space (most commonly in low Earth orbit) for an extended period of time, and to which other spacecraft or payloads can dock. A space facility is distinguished from other spacecraft used for human spaceflight by typically lacking major propulsion or landing systems. Instead, other vehicles transport people and cargo to and from space facilities. Currently, two manned space facilities are currently in orbit; the International Space Station (ISS), and China's Tiangong 1. Previous stations include the Almaz and Salyut series, Skylab, and most recently, Mir. Future space facilities may include the SpaceX Dragonlab and Bigelow aerospace Commercial Space Station.
Space facilities such as the ISS are typically used to study things such as the effects of long-term exposure to microgravity on the human body as well as to provide platforms for scientific studies and experiments involving the impact of the space environment on various physical, chemical, and biological processes, of a greater number and longer duration than is typically available on other types of space vehicles. Typically, space facilities have been designed with the intention of rotating multiple crews, with each crew member staying aboard the facility for weeks or months, but rarely more than a year. Since the ill-fated flight of Soyuz 11 to Salyut 1, all manned spaceflight duration records have been set aboard space facilities. The duration record for a single spaceflight is 437.7 days, set by Valeriy Polyakov aboard Mir from 1994 to 1995. As of 2011, three astronauts have completed single missions of over a year, all aboard Mir.
Space facilities often recover objects in space with one or more robotic arms. When the process involves recovering a delivery vehicle, it is typically called “berthing”. Using a robot arm to recover a delivery vehicle and gently attach it to a space facility enables the use of lighter vehicle-to-vehicle connection mechanisms than is possible with traditional “docking” maneuvers, where the delivery vehicle directly connects with the space facility. A typical robotic arm is controlled by a computer by activating individual step motors or actuators connected at each joint. At a minimum, a robotic arm has a single segment and a joint at each end. Robotic arms often use motion sensors to regulate movement in precise increments.
Robotic arms have been in existence for several decades. Many industries utilize robotic arms to speed production, improve product assembly quality, and manipulate hazardous objects and materials. Most robotic arms in the world are designed for heavy, repetitive manufacturing work, and handle tasks that are difficult, dangerous, or boring to human beings.
Current technology robotic arms utilize capture heads incorporating mechanical grippers, where mechanical force between two or more surfaces are used to positively capture and move objects. Mechanical grippers are suitable to capture known objects of predictable size, shape, and orientation and having robust attachment surfaces.